Over the past three decades, the percentage of adults who are obese has doubled; the percentage of children who are overweight has doubled; and the percentage of adolescents who are overweight has tripled. Two-thirds of US adults are overweight or obese. An estimated one-third of US children and adolescents are overweight, while 17 % are obese( Reference Ogden, Carroll and Kit 1 ). Children who are obese tend to become obese adults( Reference Webber, Cresanta and Croft 2 – Reference Guo, Roche and Chumlea 4 ). Obesity contributes to the major causes of death in the USA, including atherosclerotic CVD, type 2 diabetes and some forms of cancer( Reference Calle, Rodriguez and Walker-Thurmond 5 – Reference Murphy, Calle and Rodriguez 7 ). Obesity affects quality of life, increases medical costs and increases job absenteeism in adults( Reference Bungum, Satterwhite and Jackson 8 – Reference Cawley and Meyerhoefer 13 ); direct and indirect costs associated with obesity in adults are estimated at $209 billion or 20·6 % of US healthcare expenditures( Reference Cawley and Meyerhoefer 13 ). Obesity in both children and adults is most prevalent among ethnic minority groups( Reference Mei, Scanlon and Grummer-Strawn 14 – Reference Flegal, Carroll and Kit 17 ).
The extended UNICEF care model is a framework that can be used to identify factors that affect nutrition in infancy and early childhood. This framework identifies three major sets of factors that influence child nutrition: food/economic resources; caregiver resources; community health resources( Reference Engle, Menon and Garrett 18 ). Recently, Wachs( Reference Wachs 19 ) has proposed a revised version of the extended UNICEF care model to expand the influence of three caregiver resources to include maternal education, intelligence and depression, as well as child characteristics. Wachs' revised version takes a systems approach to understand how different elements are linked to determine undernutrition in children. Wachs emphasises the importance of understanding the factors that influence outcome variability as well as the different degrees and natures of these linkages. His review included a brief discussion on how a systems perspective can also apply to the study of childhood obesity.
Maternal education, maternal intelligence and maternal depression are the three caregiver resources central to Wachs' revised version of the model. Wachs added these three caregiver resources because they are both interlinked and linked to other dimensions of the model. Wachs defined maternal education as the years of schooling achieved by the mother in the public school system. Studies have shown that higher levels of maternal education are linked to better quality and quantity of children's diet( Reference Wachs and McCabe 20 ), as well as to an increase in access to economic resources( Reference Oropesa and Landale 21 ). Additional studies have indicated that maternal education levels might mediate the process through which family income influences child nutrition( Reference Boyle, Racine and Georgiades 22 ). Moreover, mothers with higher education levels were found to more likely have a greater variety of coping strategies to supplement family nutrition under times of financial stress( Reference Pongou, Salomon and Ezzati 23 ). Finally, higher maternal education levels were found to be related to better maternal health and nutritional status. This is important because mothers with poor health or nutritional status are less likely to provide adequate nutrition for their family( Reference Winkvist 24 ).
Lower education levels have also been reported to be associated with childhood obesity( Reference Baughcum, Chamberlin and Deeks 25 – Reference Strauss and Knight 27 ), especially in children with obese mothers( Reference Lumeng and Burke 28 ). Similarly, higher levels of parental education may serve as a protective factor against childhood obesity( Reference Genovesi, Giussani and Faini 29 , Reference Padez, Mourao and Moreira 30 ). However, the relationship between parental education and childhood obesity may be moderated by ethnicity( Reference Patterson, Stern and Crawford 31 ) and culture( Reference Martorell, Khan and Hughes 32 ).
The relationship between parental education and the risk of childhood obesity may be a function of parental perceptions or parent–child interactions. For example, mothers with higher levels of education may be more accurate in their perception of their children's weight compared with those with lower levels of education( Reference Baughcum, Chamberlin and Deeks 25 , Reference Genovesi, Giussani and Faini 29 ). Lower maternal education levels have been reported to be related to more prompts for children to eat novel foods, which has been found to be a predictor of higher BMI in children( Reference Lumeng and Burke 28 ). Some studies suggest an inverse relationship between parental education and dietary fat intake( Reference Kushi, Folsom and Jacobs 33 – Reference Jacobsen and Thelle 35 ) and selection of high-fat foods( Reference Whitaker, Wright and Koepsell 36 ) by children.
Maternal intelligence was also added as a caregiver resource to Wachs' revised model. Wachs defined intelligence as an individual's ability to both modify and adapt to his or her environment. Studies have shown an association between higher levels of schooling and higher levels of intellectual performance. Wachs argued that higher intellectual functioning might act as a mediator in the aforementioned relationship between maternal education and child nutrition.
Maternal depression was the third caregiver resource added to the model by Wachs. Depressed mothers exhibit disturbed patterns of mother–infant interactions (i.e. reduced sensitivity, responsivity and interaction). These characteristics may limit the ability of a mother to respond appropriately when feeding her child( Reference Rahman, Harrington and Bunn 37 , Reference Engle and Zeitlin 38 ). Moreover, in families of low socio-economic status (SES), restriction of food choices requires greater caregiver involvement (e.g. providing the best possible nutrition at the lowest cost). Such active involvement is less likely to occur in depressed mothers( Reference Hostetter, Stowe, Lewis-Hall, Williams, Panetta and Herrera 39 ).
Wachs included social support as a mechanism that affected caregiver resources. Social support was defined as the mother's social network of family and friends, who through their interactions can enhance her ability to function under stressful conditions. Studies have shown that higher levels of social support positively affect mothers' ability to care for their family during times of economic stress( Reference Wachs and McCabe 20 ). Women with lower levels of social support were found to be at an increased risk of maternal depression( Reference Wachs and McCabe 20 ).
Finally, Wachs incorporated child characteristics into the extended UNICEF care model. The following four child characteristics were included: health; sex; age; temperament. These child characteristics interact with the other factors in the model to affect child nutrition. For example, individual differences in child temperament may directly influence child nutrition and moderate or mediate the influence of family and caregiver resources on child nutrition. Furthermore, there is evidence suggesting that maternal feeding practices vary depending on the weight of children( Reference Francis, Hofer and Birch 40 ). Mothers who perceived their daughters to be overweight reported using more restrictive feeding practices. Similarly, mothers reported using more pressure in feeding when daughters were thinner.
Overall, these patterns of findings show that other factors beyond financial resources and food availability influence child nutrition and these include many non-economic factors. Although Wachs' proposed revision offers mediating and moderating links between different elements of the extended UNICEF care model, certain limitations prevent the model from being a complete framework for childhood nutrition and subsequently childhood obesity.
Linking Wachs' version of the extended UNICEF care model to childhood obesity: emotional climate of the parent–child relationship
The effectiveness of current obesity programmes (based on published reviews) is quite modest( Reference Stice, Shaw and Marti 41 – Reference Summerbell, Waters and Edmunds 44 ), with many programmes demonstrating no significant reduction in weight. Including family factors in our understanding of the interrelated constructs affecting childhood obesity is clearly needed so that effective obesity prevention programmes can be developed. An important family construct that has not been included in Wachs' revised version of the extended UNICEF care model is the emotional climate of the parent–child relationship. Parents are the gatekeepers within their households making certain foods available/accessible or not and providing modelling while consuming those foods in front of their children( Reference Mitchell, Farrow and Haycraft 45 , Reference Birch and Davison 46 ). Furthermore, it is well known that parent–child feeding interactions affect children's weight status( Reference Faith, Scanlon and Birch 47 ). However, the emotional quality of the parent–child relationship may play an important role in what is transmitted to the child within the family context, especially when it comes to feeding.
Certain factors may affect the quality of the parent–child relationship. Depression (which already appears in Wachs' revised model) clearly plays a role in parent–child interactions( Reference Brody and Flor 48 ) and is commonly observed among mothers of young children( Reference Brody and Flor 48 ). However, other risk factors (as has been mentioned above) such as stress, culture and low SES interact with maternal depression to affect children. Women of ethnic minorities and low SES exhibit the highest rates of maternal depression as they more frequently experience negative life events and have fewer resources to cope with these events( Reference Hall, Williams and Greenberg 49 – Reference Hopkins, Marcus and Campbell 54 ). These mothers are at a risk of low self-esteem( Reference Sachs, Hall and Pietrukowicz 55 ), chronic stressors and depressive symptoms( Reference Hall, Williams and Greenberg 49 ) and providing inconsistent, inappropriate discipline( Reference Sack, Mason and Higgins 56 , Reference Susman, Trickett and Iannotti 57 ). Furthermore, maternal depression has been reported to be associated with increased pressure on daughters to eat more food( Reference Francis, Hofer and Birch 40 ) and higher use of maternal restrictive feeding( Reference Francis, Hofer and Birch 40 , Reference Farrow and Blissett 58 ), which may play a role in childhood obesity.
The aim of the present narrative review paper is to extend the UNICEF care model to focus on childhood obesity and its associated risks with an emphasis on the emotional climate of the parent–child relationship within the family. Elevated levels of familial risk (such as stress and depression) can interfere with parents' abilities to provide appropriate parenting/feeding within the family context( Reference Brody and Flor 48 ). Based on Wachs' review, we modified the extended care model by explicitly integrating new linkages (i.e. parental feeding styles, stress, depression and mother's own eating behaviour) that have been found to be associated with the development of children's eating behaviours and risk of childhood obesity (Fig. 1). This new model, applying the systems approach to childhood obesity, combines sets of literature across multiple disciplines including developmental psychology, clinical psychology and nutrition. These new linkages are based on studies that were not incorporated in the original UNICEF model, but suggest important implications for childhood obesity. This review paper focuses on two narrative reviews: (1) relationships between parental feeding styles and children's eating behaviours and weight status (Table 1) and (2) relationships between maternal mental health and parental feeding behaviours (Table 2). Other linkages are discussed briefly. These extended links are depicted in a reformulation of Wachs' model shown in Fig. 1. This research offers important advancements to the scientific understanding of familial influences on children's eating behaviours and weight status.
Fig. 1 Adaptation of the extended UNICEF care model. * Family financial resources will mediate the influence of maternal education and moderate the influence of social support. † Child age may moderate the influence of family economic–nutrition resources. Double-headed arrows indicate bidirectional influences and arrows intersecting other arrows indicate mediation of moderation processes.
Table 1 Relationships between parental feeding styles and children's eating behaviours and weight status
CFSQ, Caregiver's Feeding Styles Questionnaire; CFQ, Child Feeding Questionnaire; PDI, Parenting Dimensions Inventory; CBQ, Child Behaviour Questionnaire; PANAS, Positive and Negative Affect Schedule; CES-D, Center for Epidemiological Studies-Depression Scale; PSS, Perceived Stress Scale.
Table 2 Relationships between maternal mental health and parental feeding behaviours
GSI, Global Severity Index; BSI, Brief Symptoms Inventory; CFQ, Child Feeding Questionnaire; CES-D, Center for Epidemiological Studies-Depression Scale; CFSQ, Caregiver's Feeding Styles Questionnaire; NICHD SECCYD, National Institute of Child Health and Human Development Study of Early Child Care and Youth Development; PSS, Perceived Stress Scale; PRIME-MD (PHQ), Primary Care Evaluation of Mental Disorders Patient Health Questionnaire; STAI, State–Trait Anxiety Inventory; FYB, Feeding Your Baby; IFQ, Infant Feeding Questionnaire; DASS, Depression Anxiety and Stress Scale.
The emotional climate of the parent–child feeding relationship: a new paradigm for childhood obesity
A distinct research path has emerged in the obesity literature associating general parenting styles with children's overweight status( Reference Rhee, Lumeng and Appugliese 59 ). A general parenting style refers to the overall attitude and emotional climate that a parent creates with his or her child( Reference Baumrind and Damon 60 , Reference Maccoby, Martin and Mussen 61 ). Parents are categorised into one of the four parenting styles based on dimensions of demand/control and response/nurturance: authoritative (high demand/high response), characterised by parental involvement, nurturance and structure; authoritarian (high demand/low response), characterised by restrictive, punitive and power-assertive behaviours; permissive/indulgent (low demand/high response), characterised by warmth and acceptance in conjunction with a lack of monitoring; uninvolved (low demand/low response), characterised by little control and involvement.
Rhee et al. ( Reference Rhee, Lumeng and Appugliese 59 ) found childhood obesity to be most prevalent in children with parents having an authoritarian general parenting style – a finding consistent with an earlier work on high parental control of children's food intake and eating self-regulation( Reference Birch, Fisher and Davison 62 ). The permissive/indulgent general parenting style was also found to be associated with an increased risk of childhood obesity( Reference Rhee, Lumeng and Appugliese 59 , Reference Chen and Kennedy 63 , Reference Wake, Nicholson and Hardy 64 ). These findings suggest that both high control and low control in parenting are a risk factor for childhood obesity.
A small number of studies have examined the relationship between general parenting styles and children's eating behaviours. The uninvolved general parenting style (also referred to as the rejecting style) was found to be negatively associated with children's fruit and vegetable intake( Reference Rodenburg, Oenema and Kremers 65 , Reference Franchini, Poinhos and Klepp 66 ), while the permissive general parenting style was found to be positively associated with it( Reference Franchini, Poinhos and Klepp 66 ). However, a positive association between the authoritative general parenting style and children's fruit and vegetable intake has been the most consistent in the literature( Reference Rodenburg, Oenema and Kremers 65 , Reference Lytle, Varnell and Murray 67 – Reference Pearson, Atkin and Biddle 69 ). The authoritative general parenting style was also found to be negatively associated with children's high-fat and/or high-sugar food intake( Reference Chen and Kennedy 63 , Reference Pearson, Atkin and Biddle 69 , Reference Van der Horst, Kremers and Ferreira 70 ).
More recently, the concept of feeding styles has been introduced into the literature, which embeds how parents interact with their children around eating within the general parenting style framework. Similar to general parenting styles, a feeding style refers to the overall attitude and emotional climate that a parent creates with his or her child during eating episodes, which in turn affects the child's eating behaviour. This relationship is depicted in Fig. 1.
The Caregiver's Feeding Styles Questionnaire( Reference Hughes, Power and Orlet Fisher 71 ) measures styles of feeding along two dimensions: parental demandingness and responsiveness regarding children's eating behaviour. Demandingness refers to the extent to which parents are demanding of their children in eating episodes, while responsiveness refers to the extent to which parents show sensitivity towards their children's needs in the eating context. Similar to general parenting styles, differences in the two dimensions result in four styles of parental feeding: authoritative (high demand/high response), characterised by reasonable nutritional demands and feeding structure, as well as sensitivity towards the child's needs; authoritarian (high demand/low response), characterised by controlling feeding practices with little sensitivity towards the child's needs; indulgent (low demand/high response), characterised by a lack of rules and structure regarding feeding allowing the child the freedom to determine his or her nutritional intake; uninvolved (low demand/low response), characterised by a lack of control and involvement in feeding.
We searched a variety of databases for empirical studies on the relationship between maternal mental health and/or parent–child feeding behaviours and/or children's eating behaviours and/or children's weight status using the following search strategy: (maternal depression and/or life stress and/or maternal stress) and (‘parenting styles’ and/or ‘feeding practices’ and/or ‘feeding styles’ and/or ‘authoritarian’ and/or ‘authoritative’ and/or ‘indulgent’). Most of the studies found evaluated additional variables such as infant temperament, maternal demographics and breast-feeding behaviour. However, for the purposes of this narrative review, the information was divided into two tables, specifically focusing on the relationships between parental feeding styles and children's eating behaviours and weight status (Table 1) and the relationships between maternal mental health and parental feeding styles (Table 2). For both reviews, the information tabulated includes the following: authors and year of publication; study design; subject characteristics; maternal mental health assessment used; parent–child feeding behaviour assessment used; variables used for adjustment; main findings (from the fully adjusted models).
A number of studies across the child nutrition literature have reported findings linking parental feeding styles and children's eating behaviours and weight status (Table 1). Across a series of studies involving African American, White and Hispanic low-income families with children aged 3–11 years, the indulgent feeding style was found to be associated with higher weight status in children( Reference Hughes, Power and Orlet Fisher 71 – Reference Tovar, Hennessy and Pirie 75 ). Furthermore, the indulgent feeding style was found to be associated with self-selected portion sizes and intake in children aged 4–6 years( Reference Fisher, Birch and Zhang 76 ), a lower intake of fruits, vegetables and dairy foods in low-income preschoolers( Reference Hoerr, Hughes and Fisher 77 ), and a higher intake of low-nutrient, energy-dense snacks in rural low-income ethnically diverse children( Reference Hennessy, Hughes and Goldberg 78 ). The uninvolved feeding style was also found to be associated with a higher intake of energy-dense foods in preschoolers( Reference Hoerr, Hughes and Fisher 77 ). Conversely, the authoritative feeding style was found to be associated with a lower intake of low-nutrient, energy-dense snacks in children( Reference Hennessy, Hughes and Goldberg 78 ). Details regarding the methods and specific results from these eight studies showing associations between indulgent feeding and children's eating behaviours/weight status are given in Table 1. In general, these studies support the theory that parents who are highly responsive to their children during eating episodes but do not set appropriate boundaries around food deter the development of appropriate eating behaviours that may contribute to children's weight gain.
Racial/ethnic differences have been observed across feeding styles. With regard to the two permissive feeding styles, Hispanic parents were found to more likely be indulgent, whereas African American parents were found to more likely be uninvolved( Reference Hughes, Power and Orlet Fisher 71 ). In a separate study conducted among immigrant mother–child dyads of Brazilian, Haitian or Latino descent living in the Greater Boston area, the majority of the mothers were categorised as having an authoritarian feeding style or an indulgent feeding style( Reference Tovar, Hennessy and Pirie 75 ). Moreover, among these immigrant mothers, women with higher stress scores were found to more likely express an authoritarian feeding style. More details regarding these studies are given in Table 1.
Distinct from parenting/feeding styles, feeding practices are considered more goal-oriented approaches to feeding where parents have specific aims regarding how and what they feed their children. There has been some confusion in the feeding literature regarding definitions of feeding constructs and the use of the terms styles, practices, strategies and directives to depict parent–child feeding behaviours( Reference Hughes, Frankel and Beltran 79 ). The aforementioned definitions of parenting styles, feeding styles and feeding practices will be used for the purposes of this review paper. Parent–child feeding behaviours will encompass both feeding style and feeding practice constructs.
Certain feeding practices have been shown to be detrimental to the development of appropriate eating behaviours in children. These include prompts to eat( Reference Savage, Fisher and Birch 80 ), restriction on eating certain foods( Reference Rhee 81 ), using food as a reward( Reference Rhee 81 ) and some types of modelling( Reference Savage, Fisher and Birch 80 ). The use of these practices can lead to negative consequences for children. Parents who continually prompt their children to eat during eating episodes divert attention away from their internal cues of fullness, which may cause problems with eating self-regulation( Reference Savage, Fisher and Birch 80 ). When food is used as a reward (e.g. getting dessert for eating vegetables), the reward becomes the desirable object, while the required food becomes less desirable( Reference Benton 82 ). In the long term, this could lead to a shift in neurophysiology that would sensitise the brain's mesolimbic dopamine system to crave greater quantities of the reward( Reference Al'Absi 83 , Reference Pani, Porcella and Gessa 84 ). Although modelling has been shown to have positive associations with children's intake( Reference Wang, Beydoun and Li 85 ), parents can unintentionally model unhealthy behaviours (consuming large portions or eating high-fat foods) without realising the consequences for their children. Finally, restrictive feeding practices have been shown to be counterproductive such that restricted foods become sought after by the child when the food becomes available and the parent is no longer there to restrict( Reference Savage, Fisher and Birch 80 , Reference Rhee 81 ).
Most studies examining restriction, use of rewards and modelling have been based on parents' report of their own behaviour. Many of the studies examining these constructs have done so without considering the context of their use. For example, restriction has been linked to children's behaviours in predominantly experimental studies in laboratory settings. Furthermore, in a recent study of parent–child interactions using direct observation, the use of rewards as a feeding practice was almost non-existent( Reference Power, Hughes and Goodell 86 ). Moreover, the use of eating prompts was the most common and consistent feeding practice observed in parent–child interactions during meals( Reference Power, Hughes and Goodell 86 ). More work is needed to determine whether restriction, use of rewards and modelling (highly studied individual feeding practice constructs) are commonly used in the home environment during parent–child eating episodes.
The Child Feeding Questionnaire is the most common instrument used in the childhood obesity literature to measure parental feeding practices( Reference Birch, Fisher and Grimm-Thomas 87 ). This questionnaire measures three feeding practice constructs: restriction (the extent to which parents limit their children's access to ‘unhealthy’ foods); pressure to eat (the degree to which parents attempt to make sure that their children are eating enough); monitoring (the extent to which parents keep track of their children's snack and high-fat food intake). Restriction and pressure to eat are the only two feeding practice constructs that have consistently been found to be associated with children's weight status over multiple studies( Reference Faith, Scanlon and Birch 47 , Reference Clark, Goyder and Bissell 88 ).
Maternal depression, parenting styles, and feeding styles and practices
Research regarding general parenting indicates that low levels of parental satisfaction are associated with more-controlling and less-responsive parenting styles and practices( Reference Mitchell, Brennan and Hayes 89 – Reference Simons, Beaman and Conger 91 ). Maternal depression can impair parenting practices and has been linked to less-sensitive feeding interactions with children, but existing research is based on self-reports of feeding practices. Haycraft et al. ( Reference Haycraft, Farrow and Blissett 92 ) examined the relationships between maternal self-reported symptoms of depression and observations of mothers' feeding practices during a meal occasion. Mothers who reported greater symptoms of depression were found to use more verbal and physical pressure for their children to eat and to offer more incentives or conditions in exchange for their children eating. Mothers also used more vocalisations with their children about food during the observed meal occasion when they had greater symptoms of depression. There was no link between symptoms of depression and observations of maternal use of restriction. Symptoms of depression were found to be linked to observations of mothers implementing more-controlling, less-sensitive feeding practices with their children( Reference Haycraft, Farrow and Blissett 92 ). Moreover, Hughes et al. ( Reference Hughes, Power and Orlet Fisher 71 ) found higher levels of general parental control and authoritarian feeding practices (i.e. pressuring children to eat more food and restricting them from eating certain amounts or types of foods) to be associated with authoritarian feeding styles. In contrast, higher levels of general parenting responsiveness were found to be associated with authoritative feeding styles. The influence of maternal depression over parental feeding styles, and consequently over childhood obesity, is depicted in Fig. 1.
Maternal depression, stress and feeding behaviours
In our search for articles examining maternal mental health and parental feeding behaviours, over thirty articles were reviewed; however, only eight articles were found to specifically address the relationship between maternal mental health and parental feeding. In particular, these eight studies included an assessment of maternal mental health. The major characteristics of these eight studies are summarised in Table 2.
Most of the studies were conducted in either the USA or the UK, while one study was conducted in Australia. The majority of studies had a longitudinal design, and all of them used questionnaires as their main data collection tool. Subjects were mother–infant dyads, with numbers ranging from 62 to 702 per study. Most of the subjects were White, except for the participants of a study involving immigrant mother–infant dyads.
Maternal mental health variables were measured using a variety of instruments. Of the six studies that assessed maternal mental health, two used the Brief Symptom Inventory, while two other studies used the Center for Epidemiological Studies-Depression Scale. The other questionnaires used included the Global Severity Index, the Perceived Stress Scale, the Primary Care Evaluation of Mental Disorders Patient Health Questionnaire, the Spielberger State–Trait Anxiety Inventory, and the Depression Anxiety and Stress Scale.
Parent–child feeding behaviours were assessed using a variety of questionnaires. Of the six studies that assessed parent–child feeding behaviours, five used the Child Feeding Questionnaire. The sixth study used the Caregiver's Feeding Styles Questionnaire – also used in other studies. Other questionnaires used were the Infant Feeding Questionnaire and Feeding Your Baby.
Finally, most of the studies adjusted for a wide range of potential confounding factors. Most, but not all, of the studies adjusted for well-known factors associated with depression such as breast-feeding duration, infant weight, and socio-economic factors such as education and income.
Maternal depression, stress and eating behaviours
Eating is often cited as a means of coping with stress( Reference Spillman 93 , Reference Warr and Payne 94 ). Stress affects eating behaviours in different people in different ways. Studies have demonstrated both increased (hyperphagic response) and decreased (hypophagic response) eating in response to stress( Reference Stone and Brownell 95 ). Greeno & Wing( Reference Greeno and Wing 96 ) concluded that chronic stressors tend to facilitate hypophagia, whereas acute and possibly milder stressors often result in hyperphagia. Greater stress was also found to be associated with more fatty food intake, less fruit and vegetable intake, more snacking, and a reduced likelihood of daily breakfast consumption( Reference Cartwright, Wardle and Steggles 97 ). These effects were independent of individual (sex and weight) and social (SES and ethnicity) factors. Nonetheless, some investigators are beginning to establish a link between chronic stress and overeating (especially high-fat, high-carbohydrate and comfort foods) within the African American community( Reference Jackson, Knight and Rafferty 98 ). Increased intake of snack-type foods and decreased intake of meal-type foods were found to occur with increased stress( Reference Oliver and Wardle 99 ). Stress was found to be associated with higher energy and saturated fat and sugar intakes( Reference Wardle, Steptoe and Oliver 100 ). A significant moderating effect of restrained eating, with a hyperphagic response to stress, was observed in restrained eaters, compared with no effect in unrestrained eaters( Reference Wardle, Steptoe and Oliver 100 ). In contrast, another study demonstrated that females with high scores on disinhibition significantly ate more during stress and that neither disinhibition nor restraint was associated with the relationship between eating and stress in males( Reference Weinstein, Shide and Rolls 101 ). Clearly, stress is related to eating. There is a growing body of research linking dysregulated stress physiology to an increased vulnerability to reward (i.e. dopamine)-producing behaviours (i.e. eating and drug use)( Reference Al'Absi 83 , Reference Pani, Porcella and Gessa 84 , Reference Koob and Moal 102 – Reference Sinha 104 ). We theorise that chronic exposure to stress will have a direct impact on eating behaviours and feeding styles. However, more research is needed to clarify the stress–eating association, particularly in various ethnic populations. Similar to stress, depression is associated with changes in an individual's eating behaviour. One of the diagnostic criteria for major depression is the change in eating behaviour( 105 ). The relationship between maternal depression and stress and their association with mother's own eating behaviour are depicted in Fig. 1. Moreover, preliminary investigations suggest that prenatal and postnatal depressive symptomatology experienced by the mother – along with SES – could also have a deleterious effect on her child's stress regulatory systems( Reference Davis, Glynn and Waffarn 106 – Reference Lupien, King and Meaney 108 ).
Resemblance of mother and child food consumption patterns
Family dietary practices have been shown to be an important determinant of children's diet quality. Parents are gatekeepers and can serve as role models for their children's health-related behaviours( Reference Savage, Fisher and Birch 80 , Reference Wang, Beydoun and Li 85 , Reference Golan and Crow 109 – Reference Wroten, O'Neil and Stuff 112 ), including diet. Parental food preferences( Reference Birch and Fisher 113 ) and dietary intake( Reference Wang, Beydoun and Li 85 , Reference Oliveria, Ellison and Moore 114 – Reference Hart, Raynor and Jelalian 116 ) have been shown to influence children's eating behaviours (see Fig. 1). The majority of studies have documented the impact of maternal influences on the dietary intake of young children.
Young children imitate their parents in their choice of diets( Reference Wang, Beydoun and Li 85 , Reference Anzman, Rollins and Birch 110 , Reference Hart, Raynor and Jelalian 116 ); for example, preschool children have been shown to choose healthy foods that they have seen their parents purchase( Reference Busick, Brooks and Pernecky 117 , Reference Sutherland, Beavers and Kupper 118 ). A strong positive correlation was found between the dietary intake of younger children and that of their parents than between the dietary intake of older children or adolescents and that of their parents( Reference Wang, Beydoun and Li 85 ). Stronger positive correlations have been shown between the dietary intake of parents and that of their daughters( Reference Wang, Beydoun and Li 85 , Reference Wang, Li and Caballero 119 ) than between the dietary intake of parents and that of their sons( Reference Wang, Beydoun and Li 85 , Reference Beydoun and Wang 115 ). Although there is a widespread perception of a strong resemblance in parent–child dietary intakes( Reference Rossow and Rise 120 – Reference Laskarzewski, Morrison and Khoury 123 ), surprisingly, some studies have shown that the resemblance is weak( Reference Wang, Beydoun and Li 85 ). This is probably because the eating patterns of children are influenced by a variety of factors( Reference Patrick and Nicklas 111 ), and the family environment is just one of these factors.
Evidence suggests correlations between nutrient intakes among family members( Reference Beydoun and Wang 115 , Reference Fisher, Mitchell and Smiciklas-Wright 124 ). More recently, studies have focused on familial resemblance in dietary intake patterns, such as consumption of dairy products( Reference Beydoun and Wang 115 , Reference Hoerr, Nicklas and Liu 125 , Reference Fisher, Mitchell and Smiciklas-Wright 126 ), sweetened beverages( Reference Beydoun and Wang 115 , Reference Fisher, Mitchell and Smiciklas-Wright 126 ), fruits and vegetables( Reference Wroten, O'Neil and Stuff 112 , Reference Beydoun and Wang 115 , Reference Fisher, Mitchell and Smiciklas-Wright 124 ), and snacks/sweets( Reference Wroten, O'Neil and Stuff 112 , Reference Beydoun and Wang 115 ). Parent–child dietary intake resemblance was found to vary by food group( Reference Beydoun and Wang 115 ). This is not surprising given that the majority of studies evaluated single foods or food groups in isolation and not within the context of a meal. A recent study has expanded the current literature to include an examination of resemblance in intakes of foods, within the context of a meal, among mother–child dyads from families of limited incomes( Reference Nicklas, O'Neil and Hughes 127 ). Moderate-to-strong correlations were observed between the intakes of foods consumed at the dinner meal occasion among the mother–child dyads. The foods/beverages that the mothers served themselves were a significant predictor of the type and amounts of foods that their children were served.
Children's eating behaviours and obesity
Differing eating patterns confound our understanding of the relationship between nutrient intake and chronic diseases, including obesity( Reference Randall, Marshall and Graham 128 ). Eating patterns include restaurant food consumption, beverage consumption, portion sizes, meal patterns and meal frequency, school meal participation and consumption, and diet quality. The link between children's eating behaviours and obesity is depicted in Fig. 1. Some studies have reported each of these eating pattern components and its relationship with child nutrition.
The estimated frequency of fast-food meal consumption was found to be positively associated with energy intake in women( Reference Jeffery and French 129 ). Daily energy intake away from home has increased from 23 % (1977) to 34 % (2006)( Reference Poti and Popkin 130 ). Fast foods were the largest contributor of foods prepared away from home providing 3·5 % of energy intake in 1994 and 6·1 % in 2006 in children( Reference Poti and Popkin 130 ). Children consuming fast foods were found to have higher intakes of energy, total fat, SFA and sugar than those who did not( Reference Drewnowski and Rehm 131 , Reference Powell and Nguyen 132 ). Thus, fast food consumption was found to have a negative impact on diet quality( Reference Mancino, Todd and Guthrie 133 ). Fast food restaurants contribute few servings of fruits, vegetables, whole grains and dairy foods to the diets of children( Reference Powell and Nguyen 132 , Reference Hearst, Harnack and Bauer 134 , Reference Jaworowska, Blackham and Davies 135 ). The frequency of restaurant food consumption was found to be positively associated with increased body fatness in adults( Reference McCrory, Fuss and McCallum 136 ). Obese individuals were found to choose more total food at a fast food restaurant than their leaner counterparts, but this did not occur at the other types of eating establishments studied( Reference Coll, Meyer and Stunkard 137 ). The increasing proportion of household food income spent on foods prepared away from home may help to explain the rising national prevalence of obesity.
The possible relationship between sugar-sweetened beverage consumption and obesity received a lot of attention when a 2001 prospective study reported that the consumption of sugar-sweetened beverages is associated with a 60 % increase in the risk of obesity in 11–12-year-old children( Reference Ludwig, Peterson and Gortmaker 138 ). Although this study ignited a controversial debate, several criticisms have been raised on the interpretation of the study's findings( Reference Henry and Warren 139 – Reference Bellisle and Rolland-Cachera 141 ). From 2006 to 2007, four review articles have been published( Reference Malik, Schulze and Hu 142 – Reference Bachman, Baranowski and Nicklas 145 ): two of the articles stated that there is strong evidence that sweetened beverage consumption is associated with weight status( Reference Malik, Schulze and Hu 142 , Reference Vartainian, Schewartz and Brownell 143 ); however, the other two articles concluded that the evidence is inconclusive( Reference Pereira and Jacobs 144 , Reference Bachman, Baranowski and Nicklas 145 ). Another ten review articles have been published from 2007 to 2010( Reference Gibson 146 – Reference Woodward-Lopez, Kao and Ritchie 155 ). Once again, there was no consensus regarding the evidence: five articles concluded that the evidence on the relationship between sugar-sweetened beverage consumption and weight is inconclusive( Reference Gibson 146 – Reference Monasta, Batty and Cattaneo 150 ) and the other four articles stated that the evidence is strong( Reference Olsen and Heitmann 151 , Reference Wolff and Dansinger 152 , Reference van Dam and Seidell 154 , Reference Woodward-Lopez, Kao and Ritchie 155 ). There are several reasons for the discrepancies found in studies investigating the association between sugar-sweetened beverage consumption and weight status( Reference Gibson 146 ). However, the verdict is not yet out that sugar-sweetened beverage consumption is a major eating pattern associated with obesity. As with any food, if one eats too much, it will contribute energy to the diet and will cause weight gain if energy intake exceeds energy expenditure.
Only a few studies have examined the influence of portion size on intake in adults( Reference Edelman, Engell and Bronstein 156 – Reference Engell, Kramer and Zaring 159 ) and children( Reference Rolls, Engell and Birch 160 ). Adults were found to consume more food when served portions that were 1·5 times larger than a standard portion size( Reference Bradley 161 , Reference Meguid, Laviano and Rossi-Fanelli 162 ). Larger portion sizes have been shown to increase the intakes of both lean and obese adults( Reference Edelman, Engell and Bronstein 156 ). Similarly, 5-year-old children were found to consume greater amounts when presented with larger portions( Reference Rolls, Engell and Birch 160 ). Several studies have shown that providing children with larger food portions leads to significant increases in food and energy intakes( Reference Savage, Fisher and Marini 163 ). Children aged 3–5 years were found to consume more of the entrée and less of the other foods, such as fruits and vegetables, when larger entrée portions were served, resulting in an increased energy intake( Reference Savage, Fisher and Marini 163 ). Larger portion sizes could be contributing to the increasing prevalence of overweight among children and young adults( Reference Hill and Peters 164 ).
Adolescents with a consistent meal pattern (i.e. three meals a day) were found to be leaner than those with an inconsistent meal pattern( Reference Siega-Riz, Carson and Popkin 165 ). This observation is in agreement with findings from studies showing a link between obesity and skipping meals( Reference Siega-Riz, Carson and Popkin 165 – Reference Bellisle, Rolland-Cachera and Deheeger 169 ). An inconsistent meal pattern may mean skipping meals to reduce energy.
Breakfast consumption has been shown to improve nutrient intake( Reference Affenito, Thompson and Barton 170 – Reference Utter, Scragg and Mhurchu 173 ) and to be associated with lower BMI and other measures of adiposity in children( Reference Affenito, Thompson and Barton 170 , Reference Deshmukh-Taskar, Nicklas and O'Neil 172 – Reference Berkey, Rockett and Gillman 178 ). Ready-to-eat cereals( Reference Deshmukh-Taskar, Nicklas and O'Neil 172 , Reference Albertson, Affenito and Bauserman 179 – Reference Albertson, Anderson and Crockett 181 ), including pre-sweetened ready-to-eat cereal( Reference Albertson, Thompson and Franko 182 , Reference O'Neil, Zanovec and Nicklas 183 ) breakfasts, have specifically been shown to be associated with lower measures of weight and adiposity. In one study( Reference Deshmukh-Taskar, Nicklas and O'Neil 172 ), weight/adiposity parameters of individuals consuming ‘other breakfasts’ were compared with those of breakfast skippers and those consuming ready-to-eat cereal breakfasts and BMI z-scores and waist circumferences of the breakfast skippers were found to be greater than those of individuals consuming ready-to-eat cereals or ‘other breakfasts’. A recent systematic review and meta-analysis( Reference de la Hunty, Gibson and Ashwell 184 ) has concluded that evidence that regular consumption of breakfast cereals results in a lower BMI and a reduced likelihood of being overweight in children and adolescents is suggestive. However, a cumulative meta-analysis challenges the proposition that skipping breakfast leads to weight gain( Reference Brown, Bohan Brown and Allison 185 ). It is concluded that the scientific evidence is distorted by research lacking probative value and biased research reporting. More long-term trials are needed to better understand the proposed effect of breakfast consumption on obesity and potential mechanisms.
The percentage of children consuming snacks has increased from 74 % in 1977–78 to 98 % in 2003–6( Reference Piernas and Popkin 186 ). Snacks have been shown to be associated with an increased energy intake, accounting for more than 27 % of daily energy intake in children( Reference Piernas and Popkin 186 , Reference Hampl, Heaton and Taylor 187 ). In addition, snacking contributes significantly to nutrient intake( Reference Hampl, Heaton and Taylor 187 – Reference Cross, Babicz and Cushman 189 ). The relationship between snacking and childhood obesity is less clear. Nearly 15 years ago, the Booth hypothesis( Reference Booth 190 ) has stated that ‘grazing’ or multiple eating episodes between meals, rather than the traditional pattern of three meals per d, is a major contributing factor of obesity. Conversely, few studies have actually shown that snacking is negatively associated with body fatness( Reference Fabry, Fodo and Hejl 191 ) and a reduced risk of overweight and abdominal obesity( Reference Keast, Nicklas and O'Neil 192 , Reference Summerbell, Moody and Shanks 193 ). However, other studies have shown that snacking is not associated with weight status( Reference Hampl, Heaton and Taylor 187 , Reference Phillips, Bandini and Naumova 194 ) and not an independent predictor of weight gain( Reference Field, Austin and Gillman 195 ). There are several possible explanations for the inconsistent results on the association between snacking and childhood obesity. Study results may be equivocal because snack definitions have not been clearly established or are inconsistent across studies( Reference Piernas and Popkin 186 , Reference Kant and Graubard 196 – Reference Summerbell, Moody and Shanks 198 ). Moreover, snacking patterns are not homogeneous and vary considerably in their contribution to dietary intake( Reference Nicklas, O'Neil and Fulgoni V 199 , Reference Nicklas, O'Neil and Fulgoni VL 200 ).
Adaptation of the extended UNICEF care model
The aim of the present narrative review paper was to extend the UNICEF care model to focus on childhood obesity and its associated risks with an emphasis on the emotional climate of the parent–child relationship within the family (see Fig. 1). We sought to integrate previously unintegrated sets of literature across multiple disciplines including developmental psychology, clinical psychology and nutrition. In doing so, we discussed empirical evidence in support of the following links highlighted in Fig. 1: the relationships between maternal mental health (specifically depression) and parental feeding; the relationships between parental feeding styles and children's eating behaviours and weight status; the relationships between maternal stress and depression and mother's own eating behaviour; resemblance in mother–child food consumption patterns. Together, the studies reviewed herein point to the importance of considering the emotional climate of the parent–child relationship within the family in a systems approach to obesity.
Limitations and future research directions
Our narrative review revealed several limitations in the research designed to further espouse the links previously reviewed and integrated to the adaptation of the extended UNICEF care model. First, there remain clear gaps in the literature in terms of the number of studies that include maternal mental health in the emotional climate of the parent–child feeding relationship, with only six studies identified linking maternal mental health to feeding. Importantly, future studies should include measurement of main effects as demonstrated in Fig. 1 in combination with consideration of moderating and mediating effects, as there is a significant dearth of studies that test the full model. The use of structural equation modelling in this regard with large prospective sampling designs will be important to move the field forward. Second, current research is characterised by several methodological limitations such as an overreliance on self-reports as well as questionnaire-based measures. The impact of future studies may be greatly affected by the inclusion of interview-based measures of depression and stress in mothers and observational measures of feeding within the context of the family. Third, it became clear to us in conducting this narrative review that there is a serious lack of cross talk between psychology and nutrition with the direction of a lack of cross talk potentially being in the direction of a lack of integration of nutrition work in clinical psychology. No standard handbook on depression includes a section or chapter on the effects of maternal depression on children's overweight status or parent–child feeding behaviours in the household. There is a clear gap in communication that may be addressed by reviews of the current sort being published in clinical psychology and psychiatry journals. Finally, the potential effect of cultural worldviews, beliefs and practices on coping with stress and eating styles is yet to be studied with adequate specificity. Being able to effectively measure culture-specific constructs will allow for empirically driven interpretations of within-group and between-group differences.
Conclusion
Notwithstanding the limitations described above, our extension of the UNICEF model provides a roadmap for future research to stimulate cross-disciplinary research into the complex problem of obesity. It is only through a complex understanding of the aetiology of a problem that factors may be identified for targeted and effective intervention.
Acknowledgements
The authors cordially thank Lori Briones for helping with the preparation of the manuscript and Bee Wong for obtaining research articles.
This research project was supported in part by the USDA-Agricultural Research Service through specific cooperative agreement 58-6250-6-003.
The authors' contributions are as follows: T. A. N. conceptualised the research and A. F. E.-B. wrote the first draft of the manuscript; C. S., E. M. O. and S. O. H. substantially revised the manuscript with critical feedback.
Authorship responsibility: All the authors listed herein meet the criteria set by the International Committee of Medical Journal Editors. No one who might consider that he or she has a right to be an author has been excluded. Ethics Committee: Institutional Review Board for Baylor College of Medicine and Affiliated Hospitals.
The authors declare that they have no conflicts regarding this work and have no involvements that might raise the question of bias in the work reported or in the conclusions, implications and opinions stated.
